In local wireless communication systems, such as telephone systems, a base station communicates voice data between a telephone line and a remote unit, such as a headset, worn by a user. These conventional systems typically transmit data from the base station over a wide area adjacent to the base station. Moreover, these systems typically use ultrasound, radio frequency (RF), or infrared carrier signals to transmit data between transmitters and receivers in the base and remote units. These carrier signals are subject to "scattering" and may interfere with other nearby transmitters and receivers.
In addition, ultrasonic and infrared systems require a line-of-sight communication channel between transmitters and receivers which may limit their usefulness for certain short range applications. Likewise, the usefulness of RF systems for certain short range applications may be limited by a "1/r" signal decay rate, where "r" is the effective range of the transmitted RF signal.
Magnetic Induction (MI) communication systems have been used in commercial applications, such as audio loops in buildings, direct speech communication through security screens, and low-rate data links between underground equipment and surface equipment. The security screens typically include coils built into fixed desk mats on both sides of the screen. These systems have a short transmission range, thus making them more suitable for certain short range applications than their RF counterpart, but do not allow movement of one mat relative to the other.
One type of MI system provides a user with a telephone headset connected to a remote unit. The remote unit communicates with a stationary base unit at the user's desk. In such an environment, the user can move about within their workspace, resulting in an arbitrary orientation (i.e., height, distance, and angle) between the base unit and the remote unit that changes over time. It is desirable that such a system allow the user to move within a work area around the work station without a loss of, or a break in, the communication link due to such changes in orientation. It is also desirable that such a system be simple and inexpensive to implement.
Accordingly, there is a need for a simple and inexpensive wireless communication system that establishes and maintains a communication link between a base unit and a remote unit having a relative orientation to each other that changes over time.